A gas turbine engine operates to produce mechanical work or thrust. For a land-based gas turbine engine, a generator is typically coupled to the engine through an axial shaft, such that the mechanical work of the engine is harnessed to generate electricity. A typical gas turbine engine comprises a compressor, at least one combustor, and a turbine, with the compressor and turbine coupled together through the axial shaft. In operation, as air passes through multiple stages of axially-spaced rotating blades and stationary vanes of the compressor, its pressure increases. The compressed air is then mixed with fuel in the combustion section, which can comprise one or more combustion chambers. The fuel and air mixture is ignited in the combustion chamber, producing hot combustion gases, which pass into the turbine causing the turbine to rotate. The turning of the shaft also drives the generator.
The turbine comprises a plurality of rotating and stationary stages of airfoils. Due to the high temperatures experienced by the turbine components, it is necessary to provide cooling throughout the turbine airfoil. To most efficiently use the available cooling air, turbine blades often have a serpentine-like flow path through the interior of the turbine blade that extends to the blade tip and/or the trailing edge of the blade. Cooling air is then ejected through a plurality of slots in the trailing edge. Actively cooling this region is necessary because the trailing edge is the thinnest portion of the airfoil and most subject to erosion and thermal damage due to the elevated temperatures. Also, because the airfoil trailing edge is one of the thinnest regions of the airfoil, it is also a well-known location for crack initiation due to the high thermal and mechanical stresses imparted to the area. Specifically, the pedestals positioned proximate the trailing edge are a known source of crack initiation, and cracks in these areas can lead to failure of the turbine blade.